1. Field
The present disclosure relates to an organic photoreceptor, and an electrophotographic cartridge and an electrophotographic imaging apparatus each including the organic photoreceptor.
2. Description of the Related Art
Organic photoreceptors (OPCs) have advantages such as (1) good optical characteristics, including a wide optical absorption wavelength range and large optical absorption amount, (2) good electrical characteristics such as high sensitivity and stable charging characteristics, (3) a wide selection range of various source materials, and (4) are convenient to manufacture with low manufacturing costs. Given these advantages, organic photoreceptors are widely used instead of inorganic photoreceptors in copying machines, fax machines, laser printers, and multifunction peripherals (MFPs).
Recently, due to the requirements for high-speed and maintenance-free electrophotographic imaging apparatuses, there has been a demand for a photoreceptor with high durability. A conventional organic photoreceptor includes a low-molecular weight charge transporting material and an organic polymer material, such as a polycarbonate, as main components, and thus is soft. Accordingly, the surface of such organic photoreceptor may be easily worn out when repeatedly used in an electrophotographic process due to a mechanical load by a developing system or a cleaning system. In addition, due to the use of toner particles of smaller size to obtain high-quality images, there also has been a need to improve the cleaning characteristics of the photoreceptor. This need, however, may increase the hardness of a cleaning blade made of a rubber and a pressure exerted on a surface of the photoreceptor contacting the cleaning blade, and thus may further facilitate surface abrasion and damage of the photoreceptor. Such abrasion and damage of the photoreceptor may deteriorate electrical characteristics thereof, leading to a reduced sensitivity and reduced charging characteristics, and consequently to a low image concentration and poor image quality. In addition, local damage of the photoreceptor may deteriorate the cleaning characteristics of the photoreceptor, leaving a stripped stain on the produced image. Accordingly, the lifespan of the photoreceptor may depend on the rate of deterioration caused by such abrasion or damage.
Therefore, to improve the durability of the organic photoreceptor, it is desirable to reduce a surface abrasion loss and improve scratch resistance thereof, which is a prerequisite for improving the resistance to plate wear of the organic photoreceptor. Technologies for improving wear resistance include forming a protective layer on a surface of the photoreceptor using a thermocurable resin as disclosed in Japanese Patent Publication No. 2013-061625, Japanese Patent Publication No. 2012-189976, and Japanese Patent Publication No. 2009-229988.
However, these conventional technologies form a high-hardness protective layer of a photoreceptor by crosslinking a low-molecular weight multifunctional polymerizable acrylic monomer at a high crosslinking density so as to reduce surface abrasion loss of the photoreceptor. The formation of the high-hardness protective layer may reduce the surface abrasion loss of the photoreceptor due to a high surface hardness of the photoreceptor. However, as polymerizable groups (for example, acryloyl groups) of the polymerizable acrylic monomer form covalent crosslink bonds therebetween, severe shrinkage may occur due to a large intermolecular distance gap before and after curing. This shrinkage may highly increase the internal stress of the protective layer of the photoreceptor and brittleness so that the protective layer is more prone to breakage. Therefore, when a photoreceptor has a partial surface defect such as a scratch, the partial surface defect may extend over the photoreceptor, consequently resulting in large scratches or cracks and deteriorating the mechanical durability of the photoreceptor.
Thus, there remains a need in a protective layer having high hardness, high toughness, high elasticity, and good internal stress relaxation characteristics.